Properties

Properties : class member

Properties : also referred to "attributes" or "fileds"

 

declare a property:

<1> public private protected

<2> var(treated as public)

 

access to property:

<1> non-static: using ->(Object Operator)

<2> static: using ::

 

string literal:

<1>single quoted

<2>double quoted

<3>heredoc syntax

<4>nowdoc syntax

 

1. single quoted(单引号)

　　to specify a literal single quote, escape it with a backslash(\)

　　to specify a backslash, double it (\\)

<?php
echo 'this is a simple string';

// 可以录入多行
echo 'You can also have embedded newlines in 
strings this way as it is
okay to do';

// 输出： Arnold once said: "I'll be back"
echo 'Arnold once said: "I\'ll be back"';

// 输出： You deleted C:\*.*?
echo 'You deleted C:\\*.*?';

// 输出： You deleted C:\*.*?
echo 'You deleted C:\*.*?';

// 输出： This will not expand: \n a newline
echo 'This will not expand: \n a newline';

// 输出： Variables do not $expand $either
echo 'Variables do not $expand $either';
?>

 

2. double quoted

　　

　　

3. Heredoc

　　heredoc syntax: <<<

　　After this operator, an identifier is provided, then a newline. The string itself follows, and then the same identifier again to close the quotation.

<?php
/* 含有变量的更复杂示例 */
class foo
{
    var $foo;
    var $bar;

    function foo()
    {
        $this->foo = 'Foo';
        $this->bar = array('Bar1', 'Bar2', 'Bar3');
    }
}

$foo = new foo();
$name = 'MyName';

echo <<<EOT  //idetifiers -> newline
My name is "$name". I am printing some $foo->foo.   //string itself
Now, I am printing some {$foo->bar[1]}.
This should print a capital 'A': \x41
EOT;  //same idetifier
?>

 　　output

My name is "MyName". I am printing some Foo.
Now, I am printing some Bar2.
This should print a capital 'A': A

　　Heredoc text behaves just like a double-quoted string, without the double quotes

　　initialize static variables and class properties/constants

<?php
// 静态变量
function foo()
{
    static $bar = <<<LABEL
Nothing in here...
LABEL;
}

// 类的常量、属性
class foo
{
    const BAR = <<<FOOBAR
Constant example
FOOBAR;

    public $baz = <<<FOOBAR
Property example
FOOBAR;
}
?>

 

4. Nowdoc

　　Nowdocs are to single-quoted strings     what heredocs are to double-quoted strings.

　　A nowdoc is specified similarly to a heredoc, but no parsing is done inside a nowdoc.

　　A nowdoc is identified with the same <<< sequence used for heredocs, but the identifier which follows is enclosed in single quotes,

/* More complex example, with variables. */
class foo
{
    public $foo;
    public $bar;

    function foo()
    {
        $this->foo = 'Foo';
        $this->bar = array('Bar1', 'Bar2', 'Bar3');
    }
}

$foo = new foo();
$name = 'MyName';

echo <<<'EOT'
My name is "$name". I am printing some $foo->foo.
Now, I am printing some {$foo->bar[1]}.
This should not print a capital 'A': \x41
EOT;
?>

　　output

My name is "$name". I am printing some $foo->foo.
Now, I am printing some {$foo->bar[1]}.
This should not print a capital 'A': \x41

　　Unlike heredocs, nowdocs can be used in any static data context. The typical example is initializing class properties or constants:

 

 

 

Variable parsing

　　double quotes and heredoc, varible are parsed within it

　　It provides a way to embed a variable, an array value, or an object property in a string with a minimum of effort.

 

　　Simple synta　　

<?php
$juices = array("apple", "orange", "koolaid1" => "purple");

echo "He drank some $juices[0] juice.".PHP_EOL;
echo "He drank some $juices[1] juice.".PHP_EOL;
echo "He drank some juice made of $juice[0]s.".PHP_EOL; // Won't work
echo "He drank some $juices[koolaid1] juice.".PHP_EOL;

class people {
    public $john = "John Smith";
    public $jane = "Jane Smith";
    public $robert = "Robert Paulsen";
    
    public $smith = "Smith";
}

$people = new people();

echo "$people->john drank some $juices[0] juice.".PHP_EOL;
echo "$people->john then said hello to $people->jane.".PHP_EOL;
echo "$people->john's wife greeted $people->robert.".PHP_EOL;
echo "$people->robert greeted the two $people->smiths."; // Won't work
?>

　　output

He drank some apple juice.
He drank some orange juice.
He drank some juice made of s.
He drank some purple juice.
John Smith drank some apple juice.
John Smith then said hello to Jane Smith.
John Smith's wife greeted Robert Paulsen.
Robert Paulsen greeted the two .

 

　　Complex syntax  {$ or ${

<?php
// 显示所有错误
error_reporting(E_ALL);

$great = 'fantastic';

// 无效，输出: This is { fantastic}
echo "This is { $great}";

// 有效，输出： This is fantastic
echo "This is {$great}";
echo "This is ${great}";

// 有效
echo "This square is {$square->width}00 centimeters broad."; 

// 有效，只有通过花括号语法才能正确解析带引号的键名
echo "This works: {$arr['key']}";

// 有效
echo "This works: {$arr[4][3]}";

// 这是错误的表达式，因为就象 $foo[bar] 的格式在字符串以外也是错的一样。
// 换句话说，只有在 PHP 能找到常量 foo 的前提下才会正常工作；这里会产生一个
// E_NOTICE (undefined constant) 级别的错误。
echo "This is wrong: {$arr[foo][3]}"; 

// 有效，当在字符串中使用多重数组时，一定要用括号将它括起来
echo "This works: {$arr['foo'][3]}";

// 有效
echo "This works: " . $arr['foo'][3];

echo "This works too: {$obj->values[3]->name}";

echo "This is the value of the var named $name: {${$name}}";

echo "This is the value of the var named by the return value of getName(): {${getName()}}";

echo "This is the value of the var named by the return value of \$object->getName(): {${$object->getName()}}";

// 无效，输出： This is the return value of getName(): {getName()}
echo "This is the return value of getName(): {getName()}";
?>